Acoustic surveying of subterranean insect populations in citrus groves

Subterranean insect pests cause considerable economic damage but their concealment makes detection difficult. A portable acoustic system was developed and tested for its potential to rate the likelihood that trees in citrus groves were infested with Diaprepes abbreviatus (L.) larvae. The likelihood was rated independently by a computer program and an experienced listener that distinguished insect sounds from background noises. Diaprepes abbreviatus, Phyllophaga spp., or other pest insects were excavated from all 11 sites rated at high likelihood of infestation but were absent from 20 of 25 low-rated sites. There was a significant regression between the activity rate and the number of pest organisms present at recording sites although the correlation was weaker than between activity rate and likelihood of infestation. Although the system is at an early stage of development, the success of these field tests suggests that it has considerable potential as a tool to detect and monitor hidden infestations of insects in soil.     

Acoustic detection of termite infestations in urban trees

A portable, low-frequency acoustic system was used to detect termite infestations in urban trees. The likelihood of infestation was rated independently by a computer program and an experienced listener that distinguished insect sounds from background noises. Because soil is a good insulator, termite sounds could be detected easily underneath infested trees, despite the presence of high urban background noise. Termite sounds could be detected also in trunks, but background noise often made it difficult to identify termite signals unambiguously. High likelihoods of termite infestation were predicted at four live oak (Quercus virginiana Mill, Fagacae), two loblolly pine (Pinus taeda L., Pinacae), and two baldcypress (Taxodium distichum Rich. Pinacae) trees that wood-baited traps had identified as infested with Coptotermes formosanus Shiraki. Infestations also were predicted at two pine trees with confirmed recoveries of Reticulitermes flavipes (Kollar). Low likelihoods of infestation were predicted in four oak trees where no termites were found. Additional tests were conducted in anechoic environments to determine the range of acoustic detectability and the feasibility of acoustically estimating termite population levels. There was a significant regression between the activity rate and the number of termites present in a wood trap block, with a minimum detectable number of approximately 50 workers per liter of wood. The success of these field tests suggests that currently available acoustic systems have considerable potential to detect and monitor hidden infestations of termites in urban trees and around building perimeters in addition to their present uses to detect and monitor termite infestations in buildings.     

Acoustic estimation of infestations and population densities of white grubs (Coleoptera: Scarabaeidae) in turfgrass

Incidental sounds produced by Phyllophaga crinita (Burmeister) and Cyclocephala lurida (Bland) (Coleoptera: Scarabaeidae) white grubs were monitored with single- and multiple-sensor acoustic detection systems in turf fields and golf course fairways in Texas. The maximum detection range of an individual acoustic sensor was measured in a greenhouse as approximately the area enclosed in a 26.5-cm-diameter perimeter (552 cm2). A single-sensor acoustic system was used to rate the likelihood of white grub infestation at monitored sites, and a four-sensor array was used to count the numbers of white grubs at sites where infestations were identified. White grub population densities were acoustically estimated by dividing the estimated numbers of white grubs by the area of the detection range. For comparisons with acoustic monitoring methods, infestations were assessed also by examining 10-cm-diameter soil cores collected with a standard golf cup-cutter. Both acoustic and cup-cutter assessments of infestation and estimates of white grub population densities were verified by excavation and sifting of the soil around the sensors after each site was monitored. The single-sensor acoustic method was more successful in assessing infestations at a recording site than was the cup-cutter method, possibly because the detection range was larger than the area of the soil core. White grubs were recovered from >90% of monitored sites rated at medium or high likelihood of infestation. Infestations were successfully identified at 23 of the 24 sites where white grubs were recovered at densities >50/m2, the threshold for economic damage. The four-sensor array yielded the most accurate estimates of the numbers of white grubs in the detection range, enabling reliable, nondestructive estimation of white grub population densities. However, tests with the array took longer and were more difficult to perform than tests with the single sensor.     

Mapping of soil insect infestations sampled by excavation and acoustic methods.

Geostatistical analysis was used to map traditionally and acoustically sampled populations of soil invertebrates at two different times in a hayfield at Grove Hill, AL, and once in an Auburn, AL, hayfield. The distributions of nearly all the soil invertebrates and their sounds were nonrandom in all three mapping studies. The maps constructed by excavation and acoustic sampling methods were compared by correlating the estimated (kriged) soil invertebrate counts with the estimated (kriged) counts of sounds per minute (pulse rate). Acoustic and traditional estimates were positively correlated in the Auburn study. Kriged estimates for green June beetle grub counts overlapped significantly with kriged estimates of sound pulse rate (R2 = 0.47). Overlap with sound pulse rates increased slightly when other soil organisms were counted along with green June beetle grubs: estimates of sound pulse rates were significantly correlated with counts of all white grubs (R2 = 0.50), all white grubs with earthworms (R2 = 0.52), all white grubs with earthworms and earwigs (R2 = 0.59), and total invertebrates (R2 = 0.59). The correlation between acoustic and traditional estimates was not significant at Grove Hill in either year, possibly because of a lack of experience in signal analysis or because the soil invertebrates may not have generated enough sounds to be detected above the background noise levels. These results suggest that acoustic technology is a promising tool for detecting insect pests in soil, but that further study and additional analysis are needed to improve interpretation of acoustic data obtained in the field.     

Resporulation of Metarhizium anisopliae granules on soil and mortality of Tenebrio molitor: Implications for wireworm management in sweetpotato

In Australia, sweetpotato (Ipomoea batatas L.) is vulnerable to root feeding insect pests such as wireworms (e.g., Agrypnus spp.). The number of registered insecticides to control these insect pests is limited and often pest pressure, for example by wireworms, is severe close to harvest, further limiting what insecticides can be applied. Incorporating biological control agents such as entomopathogenic fungi (e.g., Metarhizium anisopliae) into integrated pest management programmes may be feasible in sweetpotato. M. anisopliae has been shown to be effective in controlling more than 200 insects and it is able to reside and grow in the rhizosphere and rhizoplane, suggesting that M. anisopliae could be a promising candidate against soil insect pests. In the study presented here, M. anisopliae was formulated into calcium alginate granules fortified with nutrients. The resporulation of the fungal granules was tested on four different soil types in the laboratory. The biocontrol efficacy of the resulting fungal growth was also examined using larval mealworms, Tenebrio molitor as a model insect in the laboratory and the glasshouse. Our results indicated that sterilised soil favoured optimal fungal resporulation, although different soil types did not have a significant effect on fungal resporulation. The resulting fungal resporulation and growth on sterilised soil caused high mortality (up to 76%) of larval mealworms in the glasshouse, whereas the fungal granules applied to non-sterile soil demonstrated poor resporulation that led to low mortality (13%) of larval mealworms. The result of this study indicates that the manipulation of microbial populations in field soil is required to enhance the fungal growth and potential insect control against wireworms in the field.     

Improved dry-fleshed sweetpotato genotypes resistant to insect pests

Thirty-five mostly dry-fleshed sweetpotato, Ipomoea batatas (L.) Lam. (Convolvulaceae), genotypes from the USDA-ARS/Clemson University sweetpotato breeding program were evaluated in nine field experiments at the U.S. Vegetable Laboratory, Charleston, SC, from 1998 to 2004. There were highly significant entry effects for percentage of uninjured roots; wireworm, Diabrotica, and Systena (WDS) index; percentage of roots damaged by sweetpotato weevil, Cylas formicarius elegantulus (Summers); percentage of roots damaged by sweetpotato flea beetle, Chaetocnema confinis Crotch); and percentage of roots damaged by white grub larvae (primarily Plectris aliena Chapin). The susceptible control, 'SC1149-19', had a significantly lower percentage of uninjured roots, a significantly higher WDS rating, and higher percentage infestations of flea beetle, grubs, and sweetpotato weevils than all other sweetpotato entries in this study. Twenty-seven genotypes had significantly less insect damage than 'Beauregard', the leading commercial orange-fleshed cultivar in the United States. In addition, 11 genotypes had significantly less insect injury than 'Picadito', a commercial boniato-type sweetpotato grown extensively in southern Florida. Overall, no genotypes were more resistant to soil insect pests than the resistant checks 'Sumor' and 'Regal'. Many of the advanced dry-flesh sweetpotato genotypes had high levels of resistance to soil insect pests, and they represent a useful source of advanced germplasm for use in sweetpotato breeding programs.     

Acoustic identification and measurement of activity patterns of white grubs in soil

Activity patterns of Phyllophaga crinita (Burmeister), Phyllophaga congrua (LeConte), Phyllophaga crassissima (Blanchard), and Cyclocephala lurida (Bland) grubs were monitored with acoustic sensors in small pots of bluegrass, Poa arachnifera Torr, at varying and constant temperatures over multiple-day periods. Experienced listeners readily distinguished three types of sound with distinct differences in frequency and temporal patterns, intensities, and durations. Of approximately 3,000 sounds detected from P. crinita larvae, 7% were identifiable as snaps, with large amplitudes and short durations typically associated with root breakage or clipping activity. Approximately 60% were identifiable as rustles, suggestive of surfaces sliding or rubbing past each other during general movement activity. Another 2% of sounds contained patterns of repeated pulses suggestive of surfaces scraping across a pointed ridge. The remaining 31% had spectral or temporal patterns that fell outside the ranges of easily recognizable sound types. Because the behavioral significance of the different sound types has not yet been fully established, the classified and unclassified sounds were pooled together in analyses of the effects of species, temperature, weight, and time of day. Grubs of all four species produced detectable sounds at rates that increased with temperature [0.45 sounds/((min)(degrees C))] and larval weight [6.3 sounds/((min)(g))]. Mean sound rates were independent of species and time of day. At temperatures <9 degrees C, mean sound rates fell below the typical levels of background noise observed under field conditions. This reduced activity at low temperatures is likely to reduce the effectiveness of acoustic monitoring in the field in cold weather. The consistency of results obtained in these tests over multiple-day periods suggests that acoustic systems have potential as tools for nondestructive monitoring of the efficacy of insect management treatments as well as for biological and ecological studies.     

Fluorescent sperm marking to improve the fight against the pest insect Ceratitis capitata (Wiedemann; Diptera: Tephritidae)

The Sterile Insect Technique (SIT) involving area-wide release of mass-reared and sterilized pest insects has proven successful to reduce, control and eradicate economically important pest species, such as the Mediterranean fruit fly (medfly). For the efficient application, effective monitoring to assess the number and mating success of the released medflies is essential. Here, we report sperm-specific marking systems based on the spermatogenesis-specific Ceratitis capitata beta2-tubulin (Ccbeta2t) promoter. Fluorescent sperm can be isolated from testes or spermathecae. The marking does not cause general disadvantages in preliminary laboratory competitiveness assays. Therefore, transgenic sperm marking could serve as a major improvement for monitoring medfly SIT programs. The use of such harmless transgenic markers will serve as an ideal initial condition to transfer insect transgenesis technology from the laboratory to field applications. Moreover, effective and easily recognizable sperm marking will make novel studies possible on medfly reproductive biology which will help to further improve SIT programs.     

昆虫与栎树的相互关系及其对栎林更新的影响

本文概述了昆虫和栎树的相互关系以及栎林种群更新研究的进展,从叶片和栎实两个方面分别分析昆虫对栎树的危害、栎树对昆虫的防御以及栎林种群更新中的问题等。（1）危害栎树的昆虫种类丰富,它们以取食叶片和栎实为主,昆虫的寄生几乎使栎实完全失去活力。（2）栎树的防御效应能影响昆虫啃食叶片的程度,被昆早寄生的栎实提前下落以及栎实产量周期性的大小年变化,能降低昆虫寄生和取食栎实所带来的损失。（3）昆虫啃食叶片降低栎树的能量利用和营养物质贮存,昆虫对栎实的寄生和取食给栎树的种子库及苗库带来压力,直接影响到栎林的种群更新,此外,昆虫对栎实的寄生也会影响脊椎动物搬运栎实时的选择取向,间接控制栎实扩散,进而影响栎树的种群更新。     

Effects of traffic-regulated street lighting on nocturnal insect abundance and bat activity

New technological developments modulate the light levels of LED street luminaires according to traffic volumes: light levels are increased given traffic and reduced in its absence. Such dimming of street lights reduces the level of artificial light at night (ALAN) and may thus contribute to mitigate light pollution. To quantify the impact of traffic-driven dimming of street lights on nocturnal insect abundance and bat activity in comparison to full light (i.e., dimming functions of luminaires switched off), we mounted 20 insect flight-interception traps and ten batloggers on street light poles along two dimmable street light sections. Insect abundance and bat activity were measured alternately with one week of full street lighting followed by a week with light levels modulated by traffic volumes. In total, 16 dimmed and 16 full-light days were investigated. Overall, traffic-driven dimming reduced light levels by 35%. Weather conditions (warm, dry nights) were the main drivers of insect abundance and bat activity, but traffic-driven dimming resulted in lower numbers of insects caught and reduced bat activity. Among insect groups, Heteroptera benefited most from dimming. For bats, urban exploiters (Pipistrellus spp.) benefited from increased availability of prey at brightly lit street lights, while less frequent species (Myotis spp.) did not benefit from street lighting. We conclude that street light dimming technology may contribute to mitigate negative effects of ALAN on nocturnal organisms, although the measure may not be efficient enough to support light-sensitive and threatened species.     

Recent Advances in Biological Control of Pest Insects by Using Viruses in China

Insect viruses are attractive as biological control agents and could be a feasible alternative to chemical insecticides in the management of insect infestations. This review describes recent advances in the development of wild-type and genetically modified viruses as insecticides. A new strategy of application of insect viruses in China is reviewed. Also, the assessment of biosafety of genetically modified Helicoverpa armigera Nucleopolyhedovirus (HearNPV) is emphasized as a case-study.     

Microwave radar detection of stored-product insects

A microwave radar system that senses motion was tested for capability to detect hidden insects of different sizes and activity levels in stored products. In initial studies, movements of individual adults or groups of Lasioderma serricorne (F.), Oryzaephilus surinamensis (L.), Attagenus unicolor (Brahm), and Tribolium castaneum (Herbst) were easily detected over distances up to 30 cm in air. Boxes of corn meal mix and flour mix were artificially infested with 5-100 insects to estimate the reliability of detection. The likelihood that a box was infested was rated by the radar system on a quantitative scale. The ratings were significantly correlated with the numbers of infesting insects. The radar system has potential applications in management programs where rapid, nondestructive targeting of incipient insect infestations would be of benefit to the producers and consumers of packaged foods.     

Field performance of a genetically engineered strain of pink bollworm

Pest insects harm crops, livestock and human health, either directly or by acting as vectors of disease. The Sterile Insect Technique (SIT)--mass-release of sterile insects to mate with, and thereby control, their wild counterparts--has been used successfully for decades to control several pest species, including pink bollworm, a lepidopteran pest of cotton. Although it has been suggested that genetic engineering of pest insects provides potential improvements, there is uncertainty regarding its impact on their field performance. Discrimination between released and wild moths caught in monitoring traps is essential for estimating wild population levels. To address concerns about the reliability of current marking methods, we developed a genetically engineered strain of pink bollworm with a heritable fluorescent marker, to improve discrimination of sterile from wild moths. Here, we report the results of field trials showing that this engineered strain performed well under field conditions. Our data show that attributes critical to SIT in the field--ability to find a mate and to initiate copulation, as well as dispersal and persistence in the release area--were comparable between the genetically engineered strain and a standard strain. To our knowledge, these represent the first open-field experiments with a genetically engineered insect. The results described here provide encouragement for the genetic control of insect pests.     

Protease inhibitors:recent advancement in its usage as a potential biocontrol agent for insect pest management

Plant derived protease inhibitors(PIs)are a promising defensin for crop im-provement and insect pest management.Although agronomist made significant efforts in utilizing PIs for managing insect pests.the potentials of PIs are still obscured.Insect ability to compensate nutrient starvation induced by dietary PI feeding using different strategies,that is,overexpression of PI-sensitive protease,expression of PI-insensitive proteases,degradation of PI,has made this innumerable collection of PIs worthless.A practical challenge for agronomist is to identify potent PI candidates,to limit insect compensatory responses and to elucidate insect compensatory and resistance mechanisms activated upon herbivory.This knowledge could be further efficiently utilized to identify potential targets for RNAi-mediated pest control.These vital genes of insects could be functionally anno-tated using the advanced gene-editing technique,CRISPR/Cas9.Contemporary research is exploiting different in silico and modern molecular biology techniques to utilize PIs in controlling insect pests efficiently.This review is structured to update recent advancements in this field,along with is chronological background.     

昆虫细胞程序性死亡的研究进展

在昆虫发育和抵抗病原微生物的入侵过程中,细胞凋亡与自噬性死亡现象十分常见。昆虫细胞凋亡的研究已经取得了许多的成果,但是有关细胞自噬程序性死亡的研究还正在深入。昆虫细胞凋亡的信号通路至少有3条：一条类似于线虫细胞的凋亡信号通路,另一条类似于哺乳动物细胞的凋亡信号通路, 还有一条不依赖于胱天蛋白酶的凋亡信号通路。在昆虫的多种组织细胞中,细胞凋亡与自噬程序性死亡在信号通路上存在互串(cross talking),可以相互促进、抑制或替代。了解昆虫细胞程序性死亡对防治害虫具有一定的意义。     

Corn earworm,Helicoverpa zea (Lepidoptera: Noctuidae) and other insect associated resistance in the maize inbred Tex6

A 2-yr field and laboratory study investigated insect resistance of the maize, Zea mays L., inbred Tex6, which has previously demonstrated resistance to Aspergillus ear rot and aflatoxin production, relative to susceptible inbred B73. Field studies indicated significantly greater resistance to insect feeding of V4-V8 growth stage Tex6 plants compared with B73 plants in both years, primarily to flea beetles (Chaetonema spp.). Field studies of natural (1999) and artificial (2000) infestations of corn earworms, Helicoverpa zea (Boddie), indicated much lower levels of kernel damage at milk stage (approximately three-fold) and smaller surviving larvae (approximately three-fold) in Tex6 compared with B73 ears. At harvest similar trends in reduction of numbers of damaged kernels per ear, as well as incidence and numbers of kernels per ear symptomatically infected by Fusarium spp. were noted. Laboratory studies indicated little difference in mortality or survivor weight of caterpillars or sap beetle adults caged with milk stage kernels of the two inbreds. However, assays with silks indicated significantly greater mortality of H. zea in both 1999 and 2000, and European corn borer, Ostrinia nubilalis (Hübner) in 1999 (only year tested) when fed Tex6 silks compared with B73 silks. Pollinated Tex6 silks were generally darker colored and more toxic than unpollinated silks. Thus, it is possible that commercially usable inbreds with resistance to insects, which also contribute to the mycotoxin problem through vectoring and damage, could be produced using Tex6 as a source.     

Entomopathogenic nematodes,a potential microbial biopesticide: mass production and commercialisation status – a mini review

Parasitic nematodes have several important attributes that make them excellent candidates for biological control of soil insects. These nematodes can be produced by in vivo by baiting technique on insects and commercially by in vitro solid/liquid culturing. Numerous insect pests on many different crops are being controlled by these insect parasitic nematodes, including root weevils, flea beetles, mint root borer, colorado potato beetle, white grubs, caterpillars and plant parasitic root nematode, e.g. root-knot nematodes. Utilisation of entomopathogenic nematodes (EPN) has raised intense interest and has been a growing concern globally mainly because of its potential efficiency, exemption from registration and other impressive attributes for utilising against the control of soil dwelling pests. This review highlights the mass production, commercialisation and utilisation of EPN as microbial biopesticide in bio-intensive pest management programmes.     

Reducing plant abiotic and biotic stress: Drought and attacks of greenbugs, corn leaf aphids and virus disease in dryland sorghum

Multi-year spatial overlay patterns of plants, insects and soil water may yield insights for management for reducing biotic and abiotic stresses in dryland crops. A study of non-irrigated grain sorghum (Sorghum bicolor (L.) Moench) was conducted in a Pullman clay loam on the semi-arid High Plain of Texas during 2002–2005. The objectives of the 4-year study were to understand the mechanisms of plant spatial and temporal responses to stress from drought, infestations of greenbug, corn leaf aphid (CLA) and maize dwarf mosaic virus (MDMV) disease and soil water content (SWC) heterogeneity, and to reduce plant biotic and abiotic stress using their underlying relationships in space and time. Infrared IRt/c sensed-canopy temperature was measured at 18 or 54 sites along transects in a 6 m × 6 m grid across the years. Greenbugs, CLA, MDMV, SWC and hyperstectral reflectance were determined at each IRt/c site. Natural infestations of greenbugs and CLA on sorghum occurred in early July and insect populations peaked in late July or early August. Insect attacks resulted in plant water stress and sorghum yield loss except a late replanting in early July in 2004. Sorghum grain yield was negatively correlated with canopy temperature, greenbug and CLA (−0.38 < r < −0.75, P < 0.05), and positively correlated with SWC and plant near infrared reflectance (0.25 < r < 0.67, P < 0.05). The IRt/c temperature decreased with SWC but increased with greenbugs and CLA (0.26 < R² < 0.64). Crosscorrelation analysis showed that these insect, crop, and soil variables were correlated in space within 48–54 m. Late planting in July or spray control in late July or early August would be options to reduce dryland sorghum water stress and yield loss from drought and insect attacks.     

Entomopathogenic nematodes to control black vine weevil (Coleoptera: Curculionidae) on strawberry.

We investigated the potential of heterorhabditid nematodes to control larvae of the black vine weevil, Otiorhynchus sulcatus (F.), in 2 field experiments in commercial strawberry plantings. In both experiments, nematodes were applied directly onto the straw mulch, or onto the soil after temporary removal of the mulch. Heterorhabditis marelatus Lui & Berry (Rhabditida: Heterorhabditidae) reduced numbers of weevil larvae and the percentage of plants infested in both experiments, irrespective of straw removal. In the 1st field experiment, a sponge-packed H. marelatus formulation produced lower numbers of O. sulcatus larvae per strawberry plant (mean O. sulcatus larvae per plant = 0.7) and proportion of infested plants (42%) compared with a vermiculite formulation (mean O. sulcatus larvae per plant = 1.8, proportion infested plants 67%) and an untreated control (mean O. sulcatus larvae per plant = 1.9, proportion infested plants 75%). In the first 2 wk after application, more H. marelatus were found in soil samples collected from plots treated with sponge-packed nematodes, than from plots treated with vermiculite-formulated nematodes. In the 2nd field experiment, sponge-packed formulations of H. bacteriophora Poinar (Rhabditida: Heterorhabditidae) and H. marelatus were tested. H. marelatus caused a reduction in both numbers of weevil larvae (mean O. sulcatus larvae per plant = 0.1) and proportion of infested plants (9%) but H. bacteriophora did not (mean O. sulcatus larvae per plant = 0.45, proportion infested plants 34%). More H. bacteriophora were recovered from soil samples than H. marelatus during the first 7 d of this experiment. However, laboratory studies revealed no difference in the persistence of these 2 nematodes in sand.     

昆虫血淋巴的收集技术与方法

血淋巴是昆虫生理生化研究的重要材料之一。文章分析归纳各类昆虫血淋巴的不同收集方法、收集前的昆虫准备以及收集后血淋巴的预处理,并结合该试验室研究阐述在收集昆虫血淋巴过程中的一些问题和经验,为能有效提取血淋巴提供一定的方法支持。